Electronic transmitter, receiver, and regenerative repeater for telegraph signals in a start-stop code



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July 8, 1958. A. SNIJDERS 2,842,616

ELECTRONIC TRANSMITTER, RECEIVER AND REGENERATIVE REPEATER F OR TELEGRAPH SIGNALS IN A START-STOP CODE Filed Nov. 24, 1952 14 Sheets-Sheet 14 IN VEN TOR: ANTUNIE ENIJDERE.

JLTTYI United States Patent l ELECTRONIC TRANSMITTER, RECEIVER, AND REGENERATIVE REPEATER FOR TELEGRAPH SIGNALS IN A START-STOP CODE Antonie Snijders, The Hague, Netherlands, assignor to Staatsbedrijf der Posterijen, Telegrafie en Telefonie, The Hague, Netherlands Application November 24, 1952, Serial No. 322,180 28 Claims. (Cl. 178--53.1)

This invention relates to 'a completely or fully electronic communication circuit. More particularly it deals with such an electronic circuit adapted for transmission, reception and/or regenerative repetition of stop-start multi-element telegraph code signals, such as for example a five-unit or element time-spaced binary code in which each code signal may also include at least one synchronizing element, such as a stop and/or start element.

The first telegraph communication circuits for multielement code signals involved mechanical means such as devices for the opening and closing of contacts, the energization of relays, and/or the moving of armatures for scanning the elements of each signal. Later this scanning was effected by means of a vibrating relay (see Oberman U. S. Patent 2,546,369) and then this vibrating relay was replaced by a multivibrator circuit with the signal elements being stored on condensers (see Van Duuren co-pending U. S. patent application Serial No. 251,270, filed October 15, 1951, for Telegraph Over Radio (TOR Junior) system). Electromechanical regenerative repeaters were disclosed in Oberman et a1. U. S. Patent No. 2,599,345, in which the scanning of the intelligence elements of each signal is elfected by means of a multivibrator and a start-stop device comprising two electron tubes and a relay.

A known fully electronic distributor is disclosed in the British Patent No. 572,884 which employs a plurality of resistors for producing the desired distributing results.

It is an object of the present invention to produce a simple, efficient, efiective and economic fully electronic communication circuit forscanning mutli-element signals.

Another object is to produce such a fullyelectronic circuit which contains less apparatus and a fewer number of electron tubes than the circuits previously known, thereby materially reducing the maintenance costs for the circuit.

Another object is to produce a fully electronic basic communication circuit which may be readily adapted for use in several different apparatus, including: (1) a transmitter to form the multi-element code signals from separate elements such as from a telegraphic code perforated tape; (2) a receiver to separate said elements from a code signal such as for the control of a telegraph code type printer; (3) a regenerative repeater to separate and reform the said elements such as for long line code telegraph circuits.

Another object is to produce such a circuit which produces signals having very small distortion, and which is sufficiently sensitive to detect incoming signals having greater distortions than those normally capable of detection in many previously known circuits, thereby permitting a fewer number of repeater circuits to be used in a given length of transmission line.

Another object is to produce such a circuit which may be adjusted as to the time-length of one ormore of its 2,842,616 Patented July 8, 1958 synchronizing elements, so as to automatically compensate for transmitters which transmit signals at too fast or too slow a rate.

Another object is to produce such a circuit which ignores false starts or pulses by measuring the length of received pulses to insure that only start pulses of a predetermined duration will instigate the circuit.

Another object is to produce such a circuit which may be adapted to automatic telegraph networks, wherein five, six, seven or even more elements per signal are transmitted, received and/or automatically regenerated and repeated.

Another object of this invention is to produce such a telegraph communication circuit in which electronic relay cells are employed, such as those described in the Snijders co-pending U. S. Patent application Serial No. 300,817, filed July 25, 1952. These electron relays involve a plurality of rectifiers connected to a junction and conducting in the same direction with respect to said junction, which junction may also be connected through a low impedance to a potential source, whereby the flow of current through a given one or more rectifiers from said junction may be controlled by the application of different potentials to the other rectifiers connected to said junction.

Generally speaking, the system of this invention can readily be adapted to a transmitter, receiver, or regenerative repeater, each of which is able to detect a plurality of consecutive equal time-length intelligence elements of a multi-element code signal, determine their polarity, store or record said polarity in memory devices, and retransmit or pass the intelligence of these polarities on without distortion, substantially immediately upon their reception by the system.

The electronic circuits employed in carrying out these functions comprise amplifiers, a start-stop circuit, a multivibrator or generator circuit, a distributor circuit, storing or memory circuits, a plurality of electronic relay cell means according to said above mentioned Snijders application Serial No. 300,817, and electrical conductors, resistances and capacitances for interconnecting said circuits. The scanning portion of the system of this invention may include an amplifier, the startstop circuit, the multivibrator and the distributor circuits and their connections. Each of these circuits, however, may be composed of one or more of a few standard types of unit circuits, each unit circuit comprising a pair of electron discharge tubes, or a double tube, some of which may be connected together to act as flip-flop, trigger or bi-stable circuit. The standard bistable or flip-flop type of circuit may be used as incoming, storing and outgoing circuits in the present system.

The start and stop circuit controls the start and stop of the scanning portion of the system in response to each multi-element code signal. This means that the multivibrator and distributor circuits may be started and stopped once for each complete code signal. In this way, synchronism with incoming signals is not required in that each signal is separately received and the circuit is shut ofif after its reception until the start element of the next following signal is received to start the circuit again. It is to be realized, however, that this stopping and starting occurs several times each second, in that one complete code "signal is usually only about milliseconds, including its start and stop elements. In the case of a transmitter system, the circuit may be automatically started a given time after each complete code signal has been transmitted.

The distributor circuit may comprise a series or chain of successively operated circuits each having a pair of tubes, all of which tubes are interconnected by electronic relay cell means connected to separate conductors or fails corresponding in number to the elements in each signal, to insure only'the operation or conductivity of one tube at a time in the whole distributor circuit. The start signal, which instigates the multivibrator, causes the multivibrator to operate the distributor circuit in synchronism and in sequence with the elements of one signal, so that as the elements of this code are received and/or transmitted, their polarity is connected through other and at least a pair of electronic relay cell means for each element in the signal, to their corresponding bistable memory or storing circuits. tcr the multivibrator has successively set up and stored each of the signals, the distributor then operates to shut-off or stop the multivibrator until the next start element in received to repeat the operation again. The storing circuits are accordingly reset by the next following element of each signal as it is received, and if the corresponding element of the next signal is not diiierent from that just received and stored, there will be no change in the condition of that storing circuit.

The code signals which are employed in the system of this invention are preferably composed of a plurality of equally time spaced elements, and each signal preferably includes at least a start element always of a given polarity and may also include a stop element always of the opposite polarity, one at each end of the multi-consecutive equally-time-spaced intelligence elements which vary in polarity according to the intelligence to be transmitted. The duration of the start element is preferably the same as that of each of the intelligence elements, and also preferably equal to that of the stop element. The start element, however, must have at least a minimum duration of half the corresponding time allotted to each intelligence element, in that the multivibrator controlling the scanning of this invention is operated to detect the polarity or condition of the elements in the code at a point substantially half way between the start and the termination of the duration of each element, or midway between leading and trailing edges of each intelligence element pulse. Thus, false start elements or pulses having durations of less than half the required time for each element of the signal, will not be responded to by the system of this invention.

The duration of the stop element at the end of each signal may be varied within limits to automatically compensate for signals which are received at too fast or too slow a rate in comparison with the normal operation of the present system. This may be controlled through a pair of electronic relay cell means and a variable capac itance connected at the end of the system which controls the start-stop circuit.

The above mentioned and other features and objects of this invention and the manner of attaining them are given more specific disclosure in the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a wave diagram of a signal having five intelligence elements preceded by a start element of negative potential and followed by a stop element of positive potential;

Fig. 2 is a schematic block diagram of the fully electronic system according to the present invention adapted for convenience to a receiver system circuit;

Fig. 3 is a wiring diagram of the standard trigger or special flip-flop circuit, which is employed several times in each of the different systems embodying the present invention as circuits VSl through VS3, and G811 through GS6 in Figs. 2, 11, 12 and 13 and circuits 181 through ISS in Figs. 12, together with some of the employed connections shown in dotted lines;

Fig. 4 represents graphs of the grid current and plate output voltages at various input voltages at different terminals of the standard circuit shown in Fig. 3;

Fig. is a wiring diagram of the start-stop circuit SSS 4 shown in Figs. 2, ll, 12 and 13, together with some of its connections shown in dotted lines;

Fig. 6 is a wiring diagram of the multivibrator generator circuit G in Figs. 2, ll, 12 and 13, together with some of its connections shown in dotted lines;

Fig. 7 represents graphs of the voltages with respect to the time for one multi-element signal at various terminals of the multivibrator circuit of Fig. 6;

Fig. 8 is a wiring diagram of the distributor circuit IV shown in Figs. 11, 12 and 13 which is a part of the sevenfold distributor circuit 7VV;

Fig. 9 is a wiring diagram of one of the distributor circuits V1, V2 and V3 shown in Figs. 11, 12 and 13 which are part of the seven-fold distributor circuit 7VV;

Fig. 10 represents diagrams of the voltages plotted against the time for one multi-element signal at various points of the receiver shown in Fig. 11, illustrating graphically the operation of this receiver in response to an incoming five-unit start-stop code signal wave;

Figs. 11 and 11 show a schematic block and circuit diagram of a receiver embodying the present invention and adapted for receiving five-unit start-stop telegraph codesignals, with the circuits already presented in Figs. 3, 5, 6, 8 and 9 being shown in blocks with their corresponding reference characters and terminals indicated on them;

Figs. 12 and 12 show a schematic block and circuit diagram of a transmitter embodying the present invention with the circuits already presented in Figs. 3, 5, 6, 8 and 9 being shown in blocks and adapted to be used in a system with the circuit of Fig. 11; and

Figs. 13, 13' and 13" show a schematic block and circuit diagram for a regenerative repeater embodying the present invention, with the circuits already presented in Figs. 3, 5, 6, 8, 9 being shown in blocks, and adapted to be used as a repeater in a long line circuit between the circuits of Figs. 11 and 12.

In order to illustrate this invention the following description by way of example is directed to systems for communicating telegraph code signals of marks and spaces, or and pulses, comprising seven equal timespaced elements. The specific systems and circuits for the reception, transmission and regenerative repetition of this type of multi-element signal now will be described in accordance with the following outline:

I. Multi-element signal (Fig. 1) II. General circuits 7 (1) Arrangement (Fig. 2) (2) Standard trigger circuit (Figs. 3 and 4) (3) Start-stop and generator circuits (Figs. 5, 6

and 7) (4) Distributor circuit (Figs. 8 and 9) III. A receiver (1) Rest condition (2) Start-stop and distributor (3) Scanning and storing IV. A transmitter (Figs. 12) V. A regenerator repeater (Figs. 13)

I. MULTI-ELEMENT SIGNAL Referring to Fig. 1 a wave form of one complete startstop code signal is graphically disclosed to be composed of seven elements, each of 20 milliseconds duration, in which the first, start or mark element is indicated as a negative pulse W and the seventh stop or space element is indicated as a positive pulse R, while the five intelligence elements I, II, III, IV and V may be either spaces R or marks W. The start and stop elements are preferably of opposite polarity from each other, however, either may be of mark potential or polarity. The duration in timelength of the seventh, last or stop element may be varied to compensate for signals which are received or transmitted at too fast or too slow a rate by permitting the leading edge of the start element of the next succeeding signal to form the trailing edge of said stop element.

However, there isa preferred; minimum limit for the .dura-' tion of one complete signal, namely about. 130 milliseconds, which duration may be controlled or adjusted by a condenser or capacitor C3 (see Fig. 11) and/or by the frequency of the multivibrator generator G. If this limit were reduced more it would reduce the regenerative capacity of the system, particularly when used as a regenerative repeater. This limit is also determined by the fact that the start element pulse must have a duration of at least 10 milliseconds before the system of this invention will respond to a signal. This feature also enables each of the intelligence signal elements to be scanned about 10 milliseconds after their leading edges, or about in their centers (see Fig. 10), which permits considerable more distortion of their pulse edges than could normally be tolerated in some previously known systems. Thus, the circuits of this invention are timed so that the first intelligence element is scanned 30- milliseconds after the leading edge of the start element of its corresponding signal.

11. GENERAL CIRCUITS (1) Arrangement In Fig. 2 is shown a general arrangement of the essential circuits involved in the system of this invention in a block diagram, which arrangement has been adapted for convenience of description to a'receiver for the signals shown in Fig. 1. This general circuit comprises the following parts:

(1) An incoming signal amplifier or pulse shaper VSl for receiving or detecting the signal wave as shown on the first or top line in Fig. 10 and reshaping it into a pair of square edged complementary waves as shown on the second and third lines of Fig. 10;

(2) A start-stop circuit SSS for starting and stopping the multivibrator or generator G;

(3) A .generator multivibrator G, preferably of 50 cycles to correspond with the 20 milliseconds duration elements of the signal received, which generator emits pulses each 10 milliseconds to operate the seven-fold distributor 7VV;

(4) The seven-fold distributor 7VV which scans the signals at the rightmoment and is connected to a plurality of electronic relay cell means through conductors 1 through 6;

(5) A second or feed-back amplifier circuit VS2 operated by the last pulse through the distributor 7VV which is connected through a feedback line 15 to the startstop circuit SSS for stopping the multivibrator G at the end of each signal of five intelligence elements; and

(6) Five memory circuits G81, G82, G83, G84 and 655 which record the results of the scanning and are connected both to the incoming signal from the amplifier V81 through conductor 16 as well as to the distributor connections through a series of electronic relay cell means the operation of which will be described in detail later in chapter III with reference to Fig. 11.

A transmitter (shown in Figs. 12) differs from a receiver as shown in Fig. 2, in that instead of the memory circuits GSl-GSS shown in Fig. 2 there are employed,

(7) Imput circuits I81, I82, I53, I84 and 155 which are first set according to the five intelligence elements I, H, III, IV and V, respectively, and then scanned by the distributor 7VV; and I (8) An additional or output amplifier circuit V83 (see Fig. 12') which compiles and transmits the collective signal wave according to that shown in Fig. 1.

A regenerative repeater (shown in Figs. 13) possesses the parts or circuits 1, 2, 3, 4, 5, 6 and 8 of the receiver and transmitter mentioned above, but does not include the imput circuits 181485, with the addition of an extra memory or storing circuits G86 for the stop element of the signal and additional electronic relay cell means for combining the outputs of the memory circuits before they are connected to the output amplifier circuit V83.

It is to be clearly understood that although the circuits of this invention are directed to a five-unit code with start and stop elements, the same principles may be extended to multi-unit codes other than five, without departing from the scope of this invention, in that such is merely a matter of duplication of the portions of the distributor, electronic relay cell means, and memory or storing circuits already shown in the general arrangement in Fig. 2.

(2) Standard trigger circuit The shaper, feed-back and output amplifier circuits VSl, VSZ and VS3, and the storing circuits GS1-GS6 and 181-185 are all standard trigger or flip-flop bi-stable circuits similar to that described in Snijders copending U. S. patent application Serial No. 300,817, filed July 25, 1952, however, a detailed wiring diagram of this trigger circuit is shown again here in Fig. 3.

This standard trigger circuit comprises a pair of electron tubes, such as double triodes Ella and Blb (which may be for example an ECC tube), which are connected by means of a number of resistors, and may also contain a pair of neon indicator lamps L1 and L2 to indicate which one of the two tubes is conducting at any given time. These two tubes Bla and Elk have a common cathode resistor R15 which may be connected through a terminal 11 to the negative pole of the battery V. The anode resistances of the tubes are connected respectively to parallel resistors R1/ R2 and R4/R5 which then may be connected through a terminal 2' to the positive pole of the battery V. Potentiometers R6/R11 and R9/R19 are connected from the anodes of the tubes Bla and Blb, respectively, to the negative pole of the battery V, with the taps or center points of these potentiometers between their respective pairs of resistors being connected to the output terminals 9 and 4', respectively, of the trigger circuit. Between these two output terminals 9' and 4' is connected a pair of resistors R12 and R18 in series with each other, which resistors may be of equal value, and the connection between them may be connected to another terminal 6' of the trigger circuit, which generally in the systems of this invention is connected to a common ground maintained at a potential between the positive and the negative poles of the battery V. Also in this standard trigger circuit are two high ohmic potentiometers R8/R16 and R7/R14 connected from the respective anodes of the tubes Bla and Blb to the negative battery pole through the terminal 11. These two potentiometers lid/R16 and Ri/Rld are in parallel with the potentiometers R6/R11 and R9/R19 mentioned above. The tap to potentiometer R8/R16 is connected to the control grid of the tube Blb and also through a resistor R17 to the ground terminal 6. The tap of the potentiometer R7/Rl4 is connected to the terminal 5' and also through a resistor R13 to the same ground terminal 6'. The control grid of the tube Bla is directly connected to the input terminal 8' and may also be connected via a resistance R10 to another input terminal 7. The anode of the tube Bla is directly connected to a terminal 10 and the anode of the tube Bib is directly connected to the terminal 3'. The gas filled or neon indicator tubes L1 and L2 are also connected to the anodes of the tubes B111 and Blb, respectively, and thence via a common resistance R3 through the terminal 2' to the positive pole of the battery V. Terminals 1' and 12' of this trigger circuit supply the current for heating the cathodes of the tubes Ella and Bib.

If the control grid of the tube B111 is strongly negative with respect to its cathode, it is non-conductive and carries no current; and via potentiometer R8/R16 a positive potential is applied to the control grid of tube Blb through resistors R3, Rl/RZ from the positive terminal 2. The tube Blb is then conductive which makes its anode voltage lower or less positive than the anode voltage of the tube Bla, so that the indicator lampor tube L2 glows and indicator lamp or tube L1 is extinguished. The output terminal 9 thus has a higher positive voltage than the output terminal 4, and terminal 6' has a voltage which is intermediate the voltages of the output terminals 9 and 4' because the resistors R12 and R18 are preferably selected to have equal ohmic values. When the potential to the control grid of the tube Bla rises or becomes more positive to a predetermined voltage, this tube Bla will become conductive placing a more negative voltage on the grid of tube Bib through resistor R8, and as a result of which the tube Blb will then become nonconductive. The indicator lamp L1 then begins to glow and the lamp L2 is then extinguished. The output terminals 9 and 4 then also interchange their voltages. The circuit is so connected that the transition from one condition to the other takes place substantially instantaneously or with a jump, or triggers, which action occurs within a small voltage range of say about 1 volt or half a volt of the predetermined control voltage at the input terminal 7 or 8. In either condition of the circuit, however, the terminal 6 has substantially the same voltage because the resistors R12 and R13 are equal. Thus, if the input terminal 7' bears a voltage that is nearly equal to the voltage of the terminal 6, i. e. slightly below or slightly above (i. e. more negative or more positive than) that on terminal 6, the condition, when tube Bla is non-conductive of the circuit changes.

This operation may be more clearly illustrated by a specific example, the results of which are shown on the graphs in Fig. 4 in this example the values of the resistances or resistors have been considered to be as follows:

and R17=270 kit. The battery V has been chosen to have a voltage of 220 volts between its positive and negative poles.

With tube B la non-conductive the output terminals 9 and 4' bear voltages of 80 volts and 60 volts, respectively, and the input voltage at terminal 8' will be lower than 70 volts; while terminal 6 has a voltage of 70 volts (see Fig. 4). If the input voltage (the abscissa) of the graph shown at B in Fig. 4 is increased above 70 volts to about 70.5 volts, the output voltage (the ordinate) at terminal 4' changes from 60 volts to 80 volts and terminal 9 changes from 80 volts to 60 volts. In the case of a further increase of the input voltage at terminal 7 or 8, the voltages occurring at the output terminals 4 and 9' remain practically unchanged as can be seen by the substantially horizontal lines 4' and 9 of the curves in Fig. 4. If the input voltage is decreased, the voltage will revert to the original condition when the input voltage reduces to about 69.5 volts (see the dot-ted lines at B in Fig. 4).

If the output terminals 9' and 4 are loaded, the voltages occurring at these terminals would change, which also would change the voltage occurring at terminal 6 because it is connected to have a voltage halfway between that at terminals 9' and 4, and since there is a coupling between the control grid of the tube Blb through a resistance R17 and the terminal 6', there would also be a change in the input voltage to tube Bib which could cause the circuit to change its condition. However, since several of these circuits must cooperate in one system according to this invention, the terminals 6' are connected together so that the voltage levels at their terminals 6' remain constant and as equal as possible.

The outputs of the tubes Bla and Blb indicated by curves 10' and 3', respectively, are disclosed in Fig. 4 to have a wider voltage range than those taken from the terminals 9' and 4' because of the resistances of the potentiometers RtS/Rll and R9/R19, respectively, through conductive and does carry current.

which terminals 9' and 4' are connected. There is also shown for comparison purposes at the top of Fig. 4 a graph of the grid current for the tube Bla with respect to the input voltages at terminal 8' to show when tube Bla is conductive with respect to the voltages at output terminals 3, 4, 9 and 10'.

The output terminal 5' (see Fig. 3), which is of high ohmic value or nature, may be connected to the input terminal 7' so that the condition of the trigger circuit remains unchanged after the controlling input voltage ias been taken away from the terminal 7' or 8'. Such a circuit connection is shown by dotted line conductor 21 and is employed in converting the standard circuit of Fig. 3 to the storing or memory circuits GS1-GS6 shown in Figs. 2, 11 and 13.

(3) Start-stop and generator circuits Detailed circuits of the start-stop circuit SSS and multivibrator or generator G are shown, respectively, in Figs. 5 and 6, with connections to some of their terminals shown in dotted lines in accordance with their normal connection in the circuits of Figs. 2, 11, 12 and 13.

The start-stop circuit shown in Fig. 5 is used for starting and stopping the multivibrator circuit shown in Fig. 6 in response to the start and stop elements of the code signal; the start element pulse being transmitted from the incoming shaper amplifier circuit VSl through an electron relay cell means to the input terminal 8" of the start-stop circuit SSS, and the stop element pulse being transmitted from the feedback amplifier VSZ through an electron relay cell means and conductor 15 also to the input terminal 8 of the start-stop circuit SSS.

For the purposes of illustration specific examples are presented of a start-stop circuit SSS and a generator circuit G, each of which circuits may comprise a double triode tube B2a/B2b and B3a/B3b, respectively, and may be composed of resistances or resistors having the following ohmic values: In Fig. 5 resistors R2ii=R23=L2 MS R21=820 kn, R22=27 k9; and in Fig. 6 resistors R36=R39=560 k9, R3 8=47 k0. There is also shown connected by dotted lines to the multivibrator or generator circuit G of Fig. 6, two condensers C1 and C2 each of about 2X10 farads or 0.02 14f. (microfarads).

The voltage at the cathode of the double triode B2a/ B2!) of the start-stop circuit SSS is about volts and the battery V has a voltage of 220 volts. If the control grid of the tube B2a has a voltage which is lower than 70 volts, this tube is non-conductive and carries no current. As a result of this condition the tube BZb is The anode of tube B21) is directly connected to output terminal 3".

Referring now to the generator G in Fig. 6, the output terminal 3" is directly connected to the generator input terminal 8", which is then connected both through a resistance R27 to a positive terminal 7" and through a resistance R33 to the control grid of the tube B3a of the generator. Thus, the grid of the tube 133a has the same negative potential with respect to its cathode as the grid of the tube B2a in circuit SSS has, it (during the worl ing of the multivibrator) the tube BSa is non-conductive. The control grid of the tube B3b in the generator is connected via resistors R34 and R29 also to the positive potential at the terminal 7". Connected at the terminal 7", between it and positive battery V, may be a variable resistor R40 by means of which the frequency of the whole multivibrator circuit of Fig. 6 may be adjusted, which in the case for scanning the signal of Fig. 1 is 50 cycles/ second. With the grid of tube B3b connected to a positive terminal 7", this tube is conductive and the indicator lamp L4 associated therewith glows.

The capacitors C1 and C2 connected, respectively, between the anode of tube B311 or terminal 3" and the grid of the tube B3a through terminal 8", and the anode of tube B3a or terminal 10 and the grid of tube B3b through terminal 5', are charged to equal voltages by the conductivity of this tube Bfib. If the voltage in the control grid of the tube BZa of the start-stop circuit SSS is increased or becomes more positive to about 70 volts, this tube 132a will become conductive and the tube B212 will be cut-off or become non-conductive. The capacitor C1 then discharges itself via the resistor R27 and the control grid voltage of tube B3a rises. After milliseconds, the tube B3a of the generator circuit G becomes conductive and its corresponding indicator lamp L3 glows, this being the time for the discharge of the condenser C1. Then the voltage drop occurring at the anode of the tube B3a is transferred by means of the capacitor C2 to the control grid of the tube B312 through resistor R34, as a result of which this tube B3b now becomes non-conductive. The capacitor C1 is now quickly recharged to the original high value via the anode resistances R26 and R31. In consequence of the discharge of capacitor 02 via the resistor R29, the control grid of tube B3b will attain the potential of its cathode again, so that this tube again becomes conductive and the tube BSa again becomes non-conductive, etc. Thus, via the time constant circuits CZ/RZ? and C1/R27 the tubes B361 and B31; alternately become conductive every 10 milliseconds to produce the pulses at its output terminal 3" forming a square wave according to that shown at G3" in Fig. 10.

The continued generation of this output wave G3 is stopped, however, by putting the tube 132a in the startstop circuit SSS of Fig. 5 in its nonconductive state again, by reducing the control grid voltage of this tube below 70 volts at its input terminal 8". This is done by a negative pulse potential, corresponding to the stop element of a signal, applied from the end of the distributor 7VV of Fig. 2 through the feed-back amplifier V82 and conductor to this terminal 8", to cause the grid of tube B212 to become more negative and to shut-off the conductivity of tube B which in turn causes the tube BZb to become conductive again and to shut-off the multivibrator generator circuit G in Fig. 6-at the end of its cycle of oscillation corresponding to the end of a complete code signal.

It is to be observed that if the tube BM in the startstop circuit becomes conductive for a shorter time than 10 milliseconds, the generator tubes B3a/B3b will not change their conductivity conditions and the generator G will not start oscillating. If desired, this interval may be shortened or lengthened in two ways: (1) by choosing the various elements, such as resistors of the startstop circuit SSS such that if the tube 32b is conductive, the control grid of the tube B3a will have a higher or lower potential than the voltage this grid had if tube B3a is non-conductive during the working of the multivibrator; or (2) by choosing the values of the condensers C1 and C2 to be unequal (but so that the multivibrator continues to work on a frequency of 50 cycles).

In Fig. 7 are shown graphs of the potentials at the points of the terminals 3, 8, 10 and 5" of the multivibrator circuit of Fig. 6, with respectto the time corresponding to an input code signal wave 8" of seven elements shown at the top of the graph. It should be noted that the difference between the potentials at the output terminals 3" and 3" corresponds to the varying charges on condenser C1, and the difference between potentials at the output terminals 10" and 5' corresponds to the varying charges on condenser C2. The cathode potentials of the two tubes 133a and B31: of the multivibrator circuit of Fig. 6 is indicated by the dot-dash line K at about 125 volts in each of these graphs. Thus, when the input voltage on terminal 8" or 5" exceeds the cathode voltage K, the tubes trip over so that the 10 tube B3a or B317, respectively, is made conductive and the other tube shuts-0E.

It should be noted that a false start pulse or a pulse less than 10 milliseconds in duration, an example of which is shown in the dotted lines at the beginning of the signal 3" at the top of graph in Fig. 7, is not of suflicient duration to completely discharge the condenser C1 or C2 to reach the cathode potential K, and accordingly any number of such false pulses less than 10 milliseconds in duration Will not start the multivibrator circuit G into operation. Thus the multivibrator circuit of Fig. 6 automatically ignores such false start pulses regardless of how often they are repeated.

If desired, between the terminals 9 and 4", a nonlinear resistor, such as NLR shown in Figs. 11 and 13, may be inserted as a result of which any voltage vari ation up to about 10% of the voltage of the battery V will not affect the behavior of the circuit. .A similar non-linear resistor NLRZ is also shown connected to the multivibrator G of Fig. 12.

(4) Distributor circuit According to the specific example of a seven element code signal taken for the description of this invention, a seven-fold distributor consisting of four double tube circuits, namely circuits IV, V1, V2 and V3, are employed in the distributor 7VV of Fig. 2, which circuits are connected as shown in Figs. ll, 12 or 13. A wiring diagram of initial circuit IV is shown in Fig. 8, and for the three remaining identical circuits V1, V2 and V3 in Fig. 9, with their double triode tubes B4a/B4b and BSa/Bfib, respectively, connected with resistances, terminals and indicator lamps L5, L6, L7.

For the purposes of illustration a specific example of such a distributor circuit is givenin which the resistances have the following ohmic values: In Fig. 8: R41=680 k0, R42=R43=R44=R5l=R51=39 k9, R4S=150 ko, R46=32 k0, R47=R48=l5 kit, and R49=8.2 M9; in Fig. 9:

and R54=680 k9, and R61=8.2 MS

In each of the four circuits IV, V1, V2 and V3 of the distributor 7VV, the anodes of each of the seven tubes Bb, a and B5]; are connected to Potentiometers comprising, respectively, resistors R44/R5ll, R57/R59 and R53/R63. The tapping points of each of these seven potentiometers are between said resistors and are connected, respectively, to the seven output terminals 4 9", 4" of said circuits. When the terminals 6 and 6 of the four circuits IV, V1, V2 and V3 are grounded, their terminals?" and 2 have a voltage of volts and terminals 11 and ll have a voltage of 70 volts, and the voltages of their said seven output terminals will be either 10 or +10 volts, according to whether the tube whose output is associated with that particular output terminal is conductive or non-conductive respectively. These seven output terminals are successively connected toseven separate conductor rails 1 through 7 (see Figs. ll, 12 or 13). These rails 1-7 are also correspondingly connected through rectifiers or electronic relay cell means G5 10, G11 16, G17 22, G23 28, G29 3d, G35 4t and G41 46 (similar to those described in the Snijders copending application Serial No. 300,817 above mentioned) to the grids of each of the other six triodes making up the distributor 7VV, so that when one of this series of seven tubes is conductive, all of the other six tubes in the series will be non-conductive, and only one of these seven tubes can be conductive at any time, and each successive pulse from the multivibrator G through the tube B40; of the circuit of Fig. 8, will successively cause the next tube in said series of seven tubes to become conductive from tube B4b to tube BSb of circuit V3. This is accomplished by the fact if one of the distributor tubes becomes conductive, a negative voltage is applied via the electron relay cell means connected to its corresponding rail to the control grids of all the other six tubes of the distributor 7VV.

The input tube B4a of the circuit in Fig. 8, has its cathode connected to the terminal 7 which terminal is connected to a common conductor 20 (see Figs. 11, 12 or 13) which is connected to the corresponding input terminal 7 of each of the circuits V1, V2 and V3. Thus the cathodes of all the tubes B4a, B4b, BSa, B5b are maintained at the same potential and connected via a common cathode resistor R48 in Fig. 8 to the negative terminal 11 The input terminal 8 of the circuit IV (and of the whole distributor 7VV) is directly connected to the control grid of tube B4a which is also connected via a resistor R45 to a negative potential to maintain a negative grid potential on the grid of tube B4a so it will carry no current.

Between each of the seven t-ubes B412, B5a and =B5b have been provided couplings each consisting of a potentiometer R67/R68 and a condenser C5 in Fig. 11, and potentiometers R69/R70, R71/R72, R73/R74, R75/R76, R77/R78 and R79/R'80 and condensers C6, C7, C8, C9, C and C11 in Fig. 11, respectively. One end of each said coupling potentiometer is connected to the anode or output terminal 3 10 or 3 of each tube and the other end is connected to a negative potential. The condensers are connected from the tap between the resistors of each potentiometer and the input terminal 8", 5 or 5 or control grid of the next succeeding tube, with the output of the last tube connected back to the input of the first tube. The condenser C5, C6, C7, C8, C9, C10 or C11 which is connected to the anode of a conductive tube bears a lower voltage than that of the other condensers.

From the first of seven impulses for each signal from the multivibrator G, the tube B4b of circuit IV becomes conductive; and the other six tubes B5a and B5b in circuits V1, V2 and V3 become non-conductive, as has been explained above. Now the next short positive impulse is applied to the control grid of the imput tube B4a of circuit IV, causing this tube B4a to draw current so that the voltage of the cathodes of all of the other six tubes 135a and B517 rises, these cathodes are connected by conductor 20 (see Figs. 11 through 13'). This causes tube B4b now to become non-conductive and its anode voltage rises and consequently the voltages of the plates of capacitor C5 also rise. The grid voltage of the tube ESL: in circuit V1 now ri'ses sufiiciently to more than counterbalance the original rise of the cathode voltage. Thus tube BSa now becomes conductive and tube 34a becomes non-conductive again, since the short positive impulse on its control grid from the multivibrator G has now disappeared. After a moment, the grid and cathode of tube BSa have the same voltage as the grid and the cathode of the tube B41) had in the beginning. Similarly the next or third positive impulse per signal from the multivibrator G which is applied to the control grid of the imput tube B4a, will cause the next tube in the series IV tube B512, to become conductive and return tube BSa to non-conductivity. From the above, it is'evident that the tube following the tube which was conductive always is the next tube to become conductive because only the grid voltage of this next tube is raised by means of the rise in the anode voltage of the preceding tube, and in no other tube does such a rise of grid voltage take place. Accordingly, every 20 milliseconds, a positive pulse is applied from the generator circuit G via capacitor C4 (-Fig. 11) to the control grid of the input tube B411, so that successively each tube of the seven-fold distributor becomes conductive for 20 milliseconds. The negative pulses from the multivibrator or generator G do not change the con- 7 12 ductivity of these tubes (see Fig. 10, lines 1V8 and 1, 2, 3, 4, 5, 6 and 7).

III. A RECEIVER Now that the details of the basic circuits employed in this invention have been described, the specific connections and details of a receiver will be described, including the electron relay cell means, which are an important and essential feature of the system of this invention. A wiring diagram for such a receiver is shown in Figs. ll and 11 in combination, in which the previously described circuits V81, V82, SSS, G, IV, VI, V2, V3, GSl, G82 G53, GS4 and GSS are represented by boxes with their terminals having corresponding numbers to those described in Figs. 3, 5, 6, 8 and 9. First it should be noted that all of the terminals 6 through 6 of all these box circuits are connected to ground. As a result of this, the input level of each circuit is adjusted to ground potential, and the output voltages at the terminals 9 4 and 4 of the distributor 7VV have values of plus 10 volts or minus 10 volts with respect to ground. This is in accordance with the specific examples mentioned above, wherein a battery of 220 volts is employed with its corresponding poles connected to all of the positive poles 2 having a +150 volts with respect to ground and the negative poles 11 of these circuits having a volts with respect to ground.

The circuits V81, VSZ and G81 through G35 are standard bi-stable trigger circuits according to those described in Fig. 3; the start-stop circuit SSS is according to Fig. 5; the multivibrator generator circuit G is according to Fig. 6; the circuit IV is according to Fig. 8, and the distributor circuits V1, V2 and V3 are according to Fig. 9.

(1) Rest condition In describing the operation of the circuits of Figs. 11 and 11' as a receiver, the arriving multi-element code signal is applied to the input terminal IN connected directly to terminal 7' of shaper-amplifier circuit VSl, which terminal has in its rest condition a positive voltage with respect to ground, due to the resistor R64. Before a signal has been received and when the system is in its rest or idle condition the seventh distributor tube 'BSb in circuit V3 is supposed to be conductive, so that the rail conductor 7 has a negative voltage of 10 volts with respect to ground, and the other rails 1-6 of the distributor circuit 7VV are positive by 10 volts with respect to ground. The control grid connected to the terminal 7 of the feed-back amplifier circuit VSZ is then negative so that the output terminals 9' and 4 of this feed-back amplifier circuit VSZ are then positive and negative, respectively. Thus with an idle or rest positive potential an input terminal '7 of circuit VSl, its output terminals 9' and 4 are negative and positive, respectively, with respect to ground.

There is shown above the feed-back amplifier circuit VSZ in Fig. 11, a pair of electron relay ce'll means each comprising rectifiers connected to a common junction, which junctions are indicated at a and b, respectively. The junction a is connected via the rectifier G1 and G2 to the terminal 9 of the input amplifier VSl and to the terminal J of the feed-back amplifier VSZ, respectively. This junction a assumes the more negative voltage of these two terminals 9 of VSl and V52, and is therefore negative. The junction b, however, receives via the rectifier G3 from the junction a a negative voltage, and via rectifier G4 from the output terminal 4 of the feedback amplifier circuit V32 also a negative voltage. Consequently, the tube 82a in the start-stop circuit SSS is non-conductive, and as has already been described, the generator G is inactive, and the seven-fold distributor 7VV remains in its seventh position as just described. 

